1. Field of the Invention
This invention relates to cementitious building blocks and more particularly to mortarless interlocking cementitious building blocks.
2. Description of the Prior Art
The use of building blocks, of the type sometimes referred to as cement blocks, concrete blocks, or cinder blocks, rather than conventional clay bricks is becoming more widespread. Such building blocks are commonly used by the construction industry for erecting walls, buildings and the like, and for purposes of this description, all such blocks will hereinafter be referred to as cementitious blocks.
The commonly used cementitious blocks are erected in tiers or rows, which are most often offset, and the individual cementitious blocks are bonded together by mortar which is interposed between the meeting horizontal and vertical faces of the blocks. The necessity of mortar bonding impairs the accuracy and speed with which such blocks can be erected, and requires a relatively high degree of skill to erect a properly aligned plurality of such blocks.
The degree of skill needed to erect these mortar bonded prior art blocks, not to mention the laborious task, has all but relegated the laying of such blocks to skilled craftsmen.
The laborious task of erecting the mortar bonded blocks and the high cost of employing skilled craftsmen has prompted the search for interlocking cementitious blocks which would ease the labor and degree of skill needed to lay and properly align a plurality of such blocks.
Therefore, there are examples in the prior art of cementitious blocks having recesses in one of the horizontal surfaces and projections extending from the opposite horizontal surface. Such interlocking blocks allow the interlocked assembly of one row of such blocks with parallel coextending rows immediately above and below that row. Many of such prior art interlocking blocks are still bonded together by mortar, and it is believed that the use of such mortar impairs, to at least some degree, the interlocking and the ease of accurately aligning such blocks. Although the degree of skill required to lay such interlocking blocks has been reduced, it is still desirable to employ a skilled craftsman as the use of mortar is still required, and the accuracy of block alignment still must be considered.
Still further, other prior art interlocking blocks are known which are mortarless, and all of those blocks have shortcomings of one sort or another. For example, some of those blocks are very heavy which, of course, creates problems for the block layer. Others are loose fitting so that the problems of alignment are not alleviated. One particular interlocking block relies on an interference fit between interlocking elements of the block to compensate for dimensional inaccuracies, and this creates assembly problems in that manually applied forces must be exerted to achieve an interference fit which sometimes involves scraping off excess materials. In many instances, building codes require that all cells or cavities within a wall of such prior art blocks be grouted solid with a cementitious material.
While the known art includes an example of a building block having eight recesses entering into the body thereof on one horizontal surface and eight projections extending from the opposite horizontal surface, those recesses and projections are so arranged that it is impossible to interlock one block with another similar block in a normal relationship. This is due to the fact that this known block does not have a relationship between its longitudinal and transverse dimensions which is critical and also because the four recesses and projections at each end of the block define an oblong rather than a square. Thus, it is impossible to interlock the four projections at one end of one block with the four recesses of another block arranged normally thereto.
It is a long standing custom to form most, if not all, cementitious building blocks with passages formed therein which extend between the horizontal faces. These passages are provided for several reasons. First, they accommodate any wiring, pipelines, and the like which are to be included in a building wall, and secondly, they materially lighten the weight of the block to facilitate shipping and handling by craftsmen and reduce the material, and thus the cost, of making the blocks. And, finally, the passages not used to accommodate wiring and pipelines, may be filled with suitable grouting material when it is desired to strengthen an erected structure. The cementitious blocks of this type normally have two passages formed therethrough which are of maximum cross section for weight considerations and to accommodate the wiring and/or pipelines, and must not be excessively large so as to lessen the load bearing capabilities of the block.
Many of the prior art interlocking blocks, as discussed above, have substantially reduced the cross sectional areas of the vertical passages formed therein due to the necessity of supporting the interlocking elements of the blocks. This, of course, increases the weight of such blocks, and reduces clearance for wiring and pipelines.
Therefore, a need exists for a new and improved mortarless interlocking cementitious building block which overcomes some of the problems and shortcomings of the prior art.